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Google
(regarding hiring an SEO company) says:
SUBMIT YOUR XML SITEMAPS TO THE SEARCH ENGINES HERE
- Ping Google
- Ping Google (Webmaster Accounts Only)
- Ping Yahoo!
- Ping ASK.COM
- Ping Moreover
INFO & TOOL LINKS
Matt Cutts of Google
Live Twitter Feed
Matt Cutts works for the Search Quality group in Google, specializing in search engine optimization issues. He is well known in the SEO community for enforcing the Google Webmaster Guidelines and cracking down on link spam. Cutts also advises the public on how to get better website visibility in Google. Matt's Blog
HTML Validation: Does your site validate? 93% of the best sites don't validate! Google doesn't validate, and it doesn't make a bit of difference if yours doesn't either.
Google Tip: To entirely prevent a page's contents from being listed in the Google web index even if other sites link to it, use a noindex meta tag. As long as Googlebot fetches the page, it will see the noindex meta tag and prevent that page from showing up in the web index.
"Question: What is validation?
Answer: How web designers try to justify over-charging for their work + pat each other on the back.
If you are a web designer (and/or want links from pretentious web designers) then validation is a great idea...it is core to the group circle-jerk amongst cool web designers. But for everyone else, it generally doesn't matter."
Some of the highest ranking, best known, most visited web sites don't validate:
ebay.com: 253 Errors, YouTube.com: 185 Errors, 41 warning(s), vatican.it: 1 Error, 4 warning(s), amazon.com: 1127 Errors, 77 warning(s), facebook.com: 43 Errors, 4 warning(s), whitehouse.gov: 10 Errors, 1 warning(s), Twitter.com: 88 Errors... and the list goes on. Search engines themselves do not validate and are not in the validation business.
Google: 39 Errors, 2 warning(s)
Bing: 12 Errors
Yahoo: 34 Errors, 8 warning(s)
Ask: 103 Errors, 26 warning(s)
Moreover: 45 Errors, 5 warning(s)